Saturday, February 25, 2017

7.2 Voltage Reference

1. This section largely looked at the difference in voltage depending on where you are measuring that difference in a circuit. Here I'm reminded of a distinction that was made earlier in the series. Technically, voltage is not the same as the electromotive force coming out of the battery. Voltage is a difference in potential.

So close to the negative post of a battery you have more electrons than you have at the positive post of a battery. The difference is the volts. Positive voltage means that the point we are measuring has fewer negative charges than the point to which we are measuring.

2. Some circuit components require "negative voltage," so circuits can be designed to supply both negative and positive voltages. Both of course have the same "zap," but one involves more electrons than the other.

symbol for ground

3. A ground is when part of the circuit runs through, say, the chassis of a car. The symbol for a ground is at the right.

Sometimes a ground doesn't complete a circuit but is a reference point. You can then measure different voltages between this point and other parts of the circuit.

The symbol for a connection to a chassis, perhaps used as a reference

Chassis ground

point is to the left.

4. A telegraph operated with a single wire over long distances, grounded at both ends. The sending telegraph connected the circuit for a short or longer moment, the ground completing the circuit on both ends, standing for a dot or a dash.